Impact tool



c. E. FITCH "IMPACT TOOL Aug. 7, 1951 5 Sheets-Sheef Filed Feb. 24, 1948C. E. FITCH Aug. 7, 1951 IMPACT TOOL 5 Sheets-Sheet 2 Filed Feb. 24,1948 C. E. FITCH IMPACT TOOL Aug. 7, A1951 5 Sheets-Sheet 5 Filed Feb.24, 1948 i i e L 7 o fw Aug. 7, 1951 c. E. FITCH 2,563,711

` IMPACTl TOOL v Filed Feb. 24, 1948 5 sheets-sheet 4 5 Sheets-Sheet 5c. E. FITCH IMPACT TOOL Aug. 7, 1951 Filed Feb. 24, 1948 Patented Aug.7, 1951 UNITED STATES PATENT OFFICE 2,563,711 intiem n eliffor Fitch.;crete, nl. Attltation 'February' 24, itis; senti i''t'i 14 Claims;

``This ir'il'lerltio'n relates to an impact tool 'and ymore particularlyto an iinpact Aclutch by ieans of which a succession 'of rotationalhainrner blows natte iinpnrtentnicgii an anvil to a driven -rneniberstcnatn a nut, bolt, screw, oi trie like which offers resistance 'torotation.

The primary objectv of the invention is to rapid;- ight'en nuts,` bolts,'screws or the like in a for werk; wilt-nett danger of stripping' 'theads or darnaging the heads thereof. v Anotherohject is to prolong theuseful life of the partsand provide, as nearly as possible, for the'full Contact of the faces of the parts during the period that thehannir blow is being struck. v still furtlierlobjct is to acelerate the'speed 'of rotation of "the hammer during its period di 'disengagementwith the anvil so that the energy stored in the hannier during thisperiodinay per; `forr useful Work during the' impact period. The aljveand other objects may be attained Meiplefiig this invention whichembodies anion@ its features a rotary anvil, a hammer ad"- l'acent saidanvil and rotatable withY relation thereto,- al 'iinpact elein'entcarried by said hami- 'an'a sutiable 'relative thereto into and out ofthe path of rotatin of the anvil, means posi# tively to attente saidimpatt `tlernenjt into the path of rotation of the anvil and meanspositively t retract said el'e'neit .froin such path after the harninerblow has been struck on Y the anvil to perlifiit the passage of theimpact element relative to tnt ntil. i a

Gther features include a shaft mounted to -r'otate about itslongitudinal anis, an anvil -fiired t6 the shaft intrmdiatewits endsandA extending radially" therefroirna harnrnervmounted for rati'n `1 theShaft adjacent the anvil, an ilfnJat pin advancing 'and rtinnetnni platemounted to rotate and slide longitudinally on the shaft adi- Ljacent thesi'd of the hanirner remote from the anvil; an iriipact pin 4carried bvthe plate and AI!"1`v"'alele through the hammer into and out of `theA-path lof inveihent of the anvil, means between the haiiiner disc andthe plate to retract the impact pinrfrom anvil-engagingpositn when thetorque on the sha-lt exceeds a predetermined value. ineans to prjt thein'pact pin into the path of nioverrient of che anvil alter it haspassed the anvil, and rans tb transnii't vr'tar'y "rnti'on "tothe plate.Y Y rne fore'goin: constitute stint of tneprineipai 'objects andadtantages of th present inven ion, others of which will become1apparefit renewing 'desciptidn and the drawings. in which et. 1 is aintentie Senna new, ninth an 4impact tool embodying the features 'ofthis in- 2 iention, snowiiig trie snine attached to n suitable nviri.

Fie. 2 is atiew similar to Fig. 1 in a plane per:

j jiilarto the plane f Fig. 1i; n Fig; 3 is Aa View similar to Fig. 1showing all the parts in 'sectin iore clearly to illustrate the deitails of construction; A l

4 is Aa transverse Setioiial View tia-lien substantially along thelinelll-dof Fig. l

Fig. 5 is `a transverse sectional view taken "sul stantially'alfine theline 5- 5 of Fig. 1;

Fign is a transverse sectional View taken sub'- Sthtially along th lllG--'G Of Fig. 1;

Fig.` 'v7 is a transverse' sectional View taken sub1 lstanti'ally alongthe line '1;1 of Fig. 1; Fi-g. `8 is a perspective View of the impactpin i advancing and 'retreating plate;

rFig. 9 isa perspective View of the plate illus- 'trated in Fig. 8showing the underside thereof; Fig. 1D is a perspective View of theanvil 'and t'oreue transmitting shaft;

Fig. 11 is a top plan view of a resilient coupling unit for the driverotor;

` Fig. l2 is 'a sectional View through the coupling element illustratedin Fig. 111;

Fig. 13 is 'a longitudinal sectional view through an inpact tool of amo'died form and ernlclodyingf` the features `of this invention;

Fig. 14 is a View similar to 13;

Fiqgf. 15 is a perspective View partially in section ofthe hydraulicpiston and cam plate em#- ployed in the 'embodiment illustrated in Fig.13;

Fig. 16 is a perspective View of the top of the pistn illustrated inFig. 15;

VFig. 17 is a longitudinal sectional view through a further modifiedform of hydraulic impact tool;

Fig. T8 is a transverse sectional View taken substantially along theline lil-I8 of Fig. 17;

Fig. 19 is a longitudinal sectional view through 'a furti-her mod'iedform of the invention;

Fig.` 20 is a longitudinal sectional View of the structure illustratedin Fig. 19 taken in a plane which lies perpendicular to that of Fig.19t;

Fig. 2l vahorizorital sectional View taken substantially along the line21421 of Fig. 19t;

Fig. 22 -is af transverse sectional view taken sub- Staritially 'loi'l'gthe line 2'2L-22 of Fig. 19;

Fi, 23 is perspective View 0f the hamlr emplyed in the modified form ofdevice illustrated Fie. 24 is n view similar to Fig. 23 f the under--siii et tn'ennnimer; and

Fig. 25fis afragnefltary perspective vier.T of the i employed in themodification illustrated in 19 and 20;

Rfering to the drawings in detail, a drive motor, designated generallyI5, has formed in the projecting end of its drive shaft I6 an annularrow of grooves forming longitudinal splines |1, and the end I8 of thecasing of the drive motor is formed with an annular row of radiallyspaced openings I9 for the reception of attaching studs 26 by means ofwhich this improved impact tool or clutch, designated generally 2|, iscoupled t0 the casing of the drive motor I5.

The impact tool or clutch designated generally 2| comprises a tubularbody 22 having formed at one end an outwardly extending annular flange23 which is pierced atspaced intervals to receive the attaching orcoupling studs 26 by which the impact tool is'connected to the motor'casing of the drive motor |5. The end of the casing 22 opposite thatcarrying the iiange 23 is provided with a tubular boss 24 into which isfitted a Suitable bushing 25 of anti-friction metal, and extendingthrough the bushing 25 isan end portion 26 of the torque shaft,designated generally 21, of this improved impact tool. The end of thetorque shaft 21 adjacent the portion 26 is squared, as at 28, so as toeffect a driving coupling between a wrench socket, screw-driver bit orother tool that is to be driven.

A 'The torque shaft 21 is best illustrated in Fig. and is providedadjacent the inner lend of the shaft portion 26 with an anvil 29carrying diametrically opposed, radially extending arms 36, each ofwhich is provided in opposite faces adjacent their outer endswitharcuate recesses 3| and 32', into which the impact pins, to be morefully hereinafter described, are received. A cylindrical .extension 33projects axially from the face of the anvil 29 opposite the cylindricalportion 26, and this cylindrical portion 33 is provided at its free endwith a squared extension 34 in to the end Vof which projects aninternally screwf threaded socket for the reception of a cap screw 35.Seated on the squared extension 34 beneath the cap screw 35 is a collar36, the outer surface 'of which is concentric with the shaft 21 to forma bearing for the drive coupling to be more ,fully hereinafterdescribed. Formed on the collar 36 andextending toward the anvil 29 is acam 31, the cam faces 38 of which are of true circular curvature andconcentric with axes which lie perpendicular to the longitudinal axis ofthe yshaft 21.

Mounted forY rotation about the cylindrical portion 33 of the shaft 21adjacent the anvil 29 is a hammer 39 which is provided at radiallyspacedpoints 180 apart with openings 40, the axes of which extendparallel to the longitudinal axis of 'the shaft. 21. Extending from theface of the hammer 39 remote from that disposed toward the anvil 29, atdiametrically opposed points adjacent the Yshaft 21, are cams 4|opposite faces of each of which slope toward the hammer 39, as at 42(Fig. 2).*A

MountedV for rotation on the shaft portion 33 of the shaft 21'betweenthe hammer 39 and the collar 36 is an impact pin advancing and re--tracting plate, designated generally 43, which comprises a `circularbody 44 having an axial bore 45 Atherein ,and provided with slots oropenings 46 between thebore 45jand the periphery, which openings arespaced 180 apart and extend parallel With the bore 45., Formed in theplate 44 between the openings 46 are arcuate slots 741, the curvatureofwhich lies concentric about the axis of the bore 45. Opening outwardlythrough the periphery of the plate and communicating with the arcuateslots 41 are radial 4 slots 48 which are located in diametricallyopposed relation and from the openings 46. Projecting from one face ofthe plate 44 in the direction of the collar 36 is a cam lug 49, andformed on the opposite face in concentric relation with the opening 45is a collar 56 having diametrically opposed, V-shaped notches 5| whichform cam faces for cooperation with the cam faces 42 of the cams 4| onthe hammer 39 in forcing the irnpact pin advancing and retracting plate43 away from the hammer 39.

Impact pins 52 are mounted to slide in the openings 46 in the hammer 39,and each of these pins is provided near one end with an annular groove53 forming a reduced neck which is adapted to be received in the slots41 in the plate 44. It will thus be seen that as the plate 44 moves awayfrom the hammer 39 under the influence of the cams 4| and the cam faceson the collar`56,.the pins `52 will be retractedinto the openings 46 inthe hammer 39 and out of the pathA of movement of the anvil 29.

Mounted for rotation about the collar 36 carried by the squared end34 ofthe shaft 21 is a coupling member, designated generally 54. Thiscoupling member comprises a body 55 opening into one end of which is asplined socket 56 for the reception of the splined end of the shaft I6,while the opposite end of the body is provided with a socket for thereception of the collar 36, as will be readily understood upon referenceto the drawings. Extending radially at diametrically opposite pointsfrom thebody 55 are arms 51 carrying drive pins 58 which extend parallelto the longitudinal axis of the shaft 21 and enter the openings 46 inthe plate 43. It will thus be seen that when rotary motion is. impartedto the shaft I6, the plate 43 will be driven inthe direction in whichthe drive shaft I6 rotates. `In some instances, it may be founddesirable to employ a drive unit, designated generally 59 in Fig. l2, inplace of the drive unit 54 in order to -absorb a certain amount of theshock of the impact tool and prevent it from being transmitted to thedrive shaft I6 of the motor I5.`

The drive unit 53 above referred to comprises a cylindrical body 69formed at one end with and internal socket 6I for the reception of thecollar 36 above referred to, and at its opposite end with a socket 62into which a ring-shaped cushion 63, of rubber or a suitable syntheticresin or plastic substance, is fitted. AnV internally splined bushing 64is fitted into the ring-shaped cushion 63 for receiving the splined endof the -drive shaft I5 of the drive motor I5. The body 66 is formed withdiametrically opposed, outwardly extending arms 65 carrying drive pins66 which correspond, in all respects, to the drive `pins 58 previouslydescribed, so that Whenrthe unit 59 is employed, theV plate 43 will bedriven by the drive pins, but shocks transmitted to the impact mechanismwill be absorbed by the cushion 63 and breakage of the drive shaft I6will be avoided. .Y Y

In the modification of the invention illustrated in Fig. 13,V a housingdesignated generally 61 is provided at one end with a coupling flangev68 for connection to the frame of the drive motor, and at its oppositeend with a tubular boss 69 having a bearing bushing 16 extendingtherethrough in which an anvil designated generally 1| is mounted torotate. The anvil 1| comprises an axial shaft12 provided intermediateits ends with radiating arms 13 which project laterally therefrom indiametrically opposite l relation. The l ower end of the anvil shaft isprovided with a squared portion 14, while its opposite end like theanvil shaft 21, has fixed thereto against rotation a cam sleeve 15carrying auc'am 16 which lies against the surface of the shaft 12 andprojects toward the squared end 14Hther'eof. 1

AMounted for rotationon the shaft 12 adja- Acent the arms 'I3 is arelatively massive hammer `designated generally 11 which comprises acylindrical body: .1Sl having formed therein an axial opening 19 throughwhich the shaft 1.2 extends'. Surrounding the axial opening and openingthrough the upperv end of the hammer in an annular channel Y8|l`wliic`hcommunicates at its inner end with longitudinal bores 9| in whichimpactpins 82 arev slidable. These impact pins are 4adapted to be projectedthrough the ends of thejopenings 8| which open through the end of thehammer adjacent the arms 13 in order to engage the arms 13 atpredetermined intervals during the operation of the device. Projectingupwardlyfrom the upper edge of the wall ofthe hammer lying between theaxial bore 19 and the annular recess 80 are oppositely disposed cams 83(Fig. 14), the purposeof which will be more fully hereinafter explained.

Mounted for rotation on the shaft 12 between the hammer 11 and the camcollar 15 is aV cam disc 84 carrying diametrically opposed cams 85 whichliel along the shaft 12 and cooperate' with the cams 83'in causing thedisc 84 to movev away from the hammer 11. Carried by the disc 84 andextending toward the hammer 11 is an annular collar 85 provided at itsend remote from the disc with an annular head 86 which is `adapted toreciprocate in the annular recess 80; This head is provided withsuitablechannels in'which annular `packing rings 81 are seated to form afluid tight junction with the wallsofAv the' recess 80. ltv will thus beseen that when the' channel 80 contains a non-compressible fluid. suchlas oil, and the disc 841s moved toward or away from the hammer, theimpact pins 82 will be moved into or out of the path of movement of thearms 13. Extending from the face of the disc 84 remote from the hammer11, and lying closely adjacent the shaft 12 is a cam 88 whichisadaptedto cooperate with the cam to move` theL plate- 84 toward thehammer at a certain interval' of movement of the parts. Formed in thedisc 84, and extending along axes parallelwith the axis of the shaft 12at diametrically spaced points are openings 89 for the reception ofdriveA` pins `90 carried by a driveunit 9| which ismountedto rotateabout the cam collar and `corresponds to the drive unit 54 previouslydescribed.

In the further modification of the device illustrated in Fig. 1'1 ananvil designated generally 92 is mounted in a housing 93 correspondingin all respects tothe housing 61, and carried by the anvil 92 atdiametrically opposed points are arms 94' which are provided withangular extensions 95 which lie substantially parallel to thelongitudinal axis of the anvil 92. The anvil 92 is also provided with ashaft 96 which cor responds in all respects to the shaft 12 previouslydescribed and rotatably mounted on theshaft 96 adjacent the arms 94 is acup-shaped hammer 91. Likethe hammer 11, the hammer 91 is provided withan annular Yrecess 98 in which a plunger head 99 is reciprocable underthe influence of a cam plate |00`which corresponds in all respects tothe cam plateili` previously deassegni cooperate with the cams on thecam plate |00 in moving the cam plate away from the hammer. Formed inthe hammer 91 at diametrically opposite points are transverse openings|0| in which impact' pins |02 are mounted to slide. impact pins areadapted to be projected radially into the path of movement of theangular ex" tensions at the ends of the arms 94 of the anvil 92, andwhen the annular recess 99 is filled with a non-compres's'ible fluid,such as oil, it is obvious that as the cam plate |00 moves toward andaway from the hammer 91, the impact pins |02` will be projected andretracted respectively.

The movements of the cam plate |00 are controlled in identically thesame manner as are the movements of the cam plate 84 and the cam plate43 previously described.

It will be understood, of course, that the cam plate |00 is driven in amanner similar to the driving of the cam plate 84 previously describedthrough the' medium of a coupling |03 and the drive pins |04 carriedthereby.

In' the modification illustrated in Figs. 19 and 2S, an anvil designatedgenerally |95 comprises aA shaft ide mounted to rotate in a suitablebearing bushing |531' mounted in a casing me which corresponds in allrespect to the casings previously described. The shaft |95 is providedintermedate its ends with outwardly extending diametrioally opposed armsISS, and like the shafts previously referred to, is provided with asquared end le to which a tool such as a wrench or screw .river isdetachably coupled. The end of the shaft opposite that carrying thesquared end |0 has fixed thereto a cam collar i carrying acam H2 whichlies adjacent the shaft and projectsl the camlcollar H3' and the camcollar is ahaminer H9 provided with diametrically opposite arcuateopenings ||1 which lie concentric about the axis of the shaft.Projecting from the face of the hammer H6 adjacent the anvil |99.

and lying along the shaft I0@ are diametrically,

opposed cams llt which are adapted to cooperate with the cams ||4 inmoving the hammer away from the anvil. Formed in the hammer beveenvopposite ends of the arcuate openings ||1 and extending along axes whichlie parallel with' -the shaft |86 are openings H9 in which impact pins|20 are fixed as by set screws l2 The face of the hammer ||6 oppositethat carrying the cams I3 is provided with a cam lug |22 (Fig. 23) whichis adapted to cooperate with the cam face ||2 of the cam collar inmoving the hammer I6 toward the anvil, and the impact pins |29 into thepath of movement of the arms |09.

Mounted for rotation about the cam collar is a drive unit |23 which isadapted to be coupled to the drive shaft of a suitable drive motor andis provided with outwardly extending diametrically opposed arms |24carrying` drive pins |25 which extend along axes which lie parallel`with` TheseV theaxis of the shaft H16, through the arcuate openings Hiand into the openings V|| in the arms ||4 of the cam collar ||3. Itw'ill thus be seen that the cam collar H3 will be driven in unison withthe drive unit |23, and by reason of the arcuate openings these pinsclear the hammer H5 so that any driving effect on the hammer is obtainedthrough the contact of the cam faces of the 'cams ||4 and IIB.

Operation In use, a suitable tool, such as a wrench socket, is fittedonto the squared end 28 of the shaft '2 and the drive member 5B iscoupled to the drive shaft IG of the motor |5. Upon setting the motorinto operation, it will be obvious that the drive pins 58 will rotatethe disc or plate d3, thus irnparting rotary motion to the hammer 39through the impact pins 52. So long as no resistance is encountered, theimpact pins will remain against the arms 39 of the anvil in the recesses3| and the nut or screw that is being worked upon will be driven with acontinuous rotary motion. As soon as the nut or screw becomes tightenough to offer resistance to rotation, the cam faces 42 working againstthe inclined faces 5| of the hammer Se and the plate 43, respectively,will cause the plate to move away from the hammer 39, thus withdrawingthe pins 52 into the ham-V mer so as to permit the hammer to rotateunder the influence of the drive motor without imparting movement to theshaft 2l. It is to be understood, of course, that the magnitude ofmovement of the plate 43 is such that the pins 52 are wholly retractedinto the openings 4U and yet the cam faces 4| and 5| never completelydisengage. The limitation of motion of the plate 43 away from the hammer39 is effected by the engagement of the cam lug 49 with the collar 35.In order to impart a hammer blow to the anvil 29, it becomes necessaryto force the pins through the openings 4i! and advance them into thepath of the arms 3i! of the anvil 29. This is accomplished by theengagement of the cam lug 48 with the cam 3l which vis so positionedwith relation to the anvil 29 that the impact pins 52 are forceddownwardly between the arms 30. By thus advancing the rapidly movingimpact pins 52 into the path of movement of the arms 30 of the anvil 29,it will be obvious that when the pins encounter the arms, the latterwill be struck a sharp blow backed by the momentum of the rotatinghammer 39 which will effectively drive the work home. Obviously, theoperation is repeated during the impact cycle of the tool. When it isdesired to remove a tightened nut, it is obvious that the shaft IG isreversed, in which event the pins 52, during the impact cycle of theapparatus, will engage in the recesses 32 in the arms 3G.

In the operation of the modified structure illustrated in Figs. 13through 18 inclusive, it will be understood that the annular recesses 3eand 88 contain fluid which as the cam plates 84 or lili) are advancedtoward their respective anvls, the impact pins 82 or |32, as the casemay be, will be projected into the path of movement of their respectiveanvils due to the displacement of the fluid by the advance of the head85 or the head 99 into its respective annular recess. The functions ofthe impact pins are identically the same as those previously described,and as the rotation is continued, the cams 83 and 85, will move the camplate away from its respective hammer, so as to retract the impact pinsand allow them to pass their respective arms.

In using the structureillustrated in Figs. 19. through 25 inclusive, theimpact pins |20 are carried by the hammer H6, which riding loirlgitudinally of the device on the drive pins |25 will move the impactpins intoand out of Vthe path of movement of the arms |09 ofthe anvil|05. 1

Throughout al1 forms of the .invention the cams between the cam plate orcam collar and the hammer will serve to retract the impact pins from thepath of movement of the arms of the anvil, while the cams on the faceof'the hammer or cam plate remote from the arms of the anvil,cooperating with the cams carried by the anvil will serve to advance theimpact pins into the path of movement of the arms of the anvils.

When the advancing and retracting plate 43 (Fig. 2) is in its raisedposition the hammer 39 is free to rotate with the lplate 43. As theplate i3 isY forced downwardly bythe cam 31 the upper cam 42 feedsdownwardly onto the lower cam 4| requiring the lower cam 42 with thehammer 39 to rotate at a greater velocity than the rotating speed of theshaft l5, and hence the motor. Thus the hammer 39 is given an additionalspin over and above that afforded by the motor just before the pins 52(Fig. 3) strike the anvil 29 resulting in greater momentum in the hammerand a greater impact force.

While in theforegoing there has been shown and described the preferredembodiments of this invention, it is to be Yunderstood that minorchanges in the details of construction, combination and arrangement ofparts may be resorted to without departing from the spirit and scope ofthe invention as claimed.

I claim: Y

1. In an impact mechanism, a rotatable anvil, a rotatable hammer, meansfor locking the two together for simultaneous rotation comprising aslidable element rotatable with said hammer and movable into the path ofsaid anvil, a motordriven element carrying said slidable element, cammeans between said motor-driven element v and said hammer element forrotating said hammer element and for retracting said slidable elementinrelation to said hammer, and cam means between the motor drivenelement and the anvil positively returning said slidable lelement intothe path of movement of said anvil.

2.l An impact mechanism comprising a rotary anvil, a hammer rotatableabout the aXis of the anvil, slidable impact pins carried by said hammerand movable into and out of the path of rotation of said anvil, amotor-driven element aligned axially with said hammer and anvil, animpact pin advancing and retracting element between said hammer and saidmotor-driven element, drive pins carried by the motor-driven element,and having driving relation with the impact pin advancing and retractingelement, said impact pin advancing and retracting element having camcoaction with said hammer element for rotating said hammer and forretracting said impact pins into said hammer, and having further camcoaction with said anvil for advancing said impact pins into the path ofmovement of said anvil.

3. An impact tool which includes a shaft mounted to rotate about itslongitudinalaxis, an anvil fixed to the shaft intermediate its ends andextending radially therefrom, a hammer mounted for rotation on the shaftadjacent the anvil,V an impact pin advancing and retracting platemounted to rotate and slide longitudinally on the' shaft adjacent theside of the hammer remote from the anvil, an impact pin carried by `theplate and movable through the hammerV into and .out lof the path ofmovement of the anvil, means'between the hammer' and the plate toretract the impact pin from anvil-engaging position after the pin hasstruck a blow on the anvil, means to project the impact pin into thepath of movement of the anvil after it has passed the anvil and means totransmit rotary motion to the plate.

4. An impact mechanism comprising an anvil, a hammer, means for lockingthe two together for simultaneous movement comprising slidable hammerpins rotatable with said hammer and movable into and out of the path ofsaid anvil, a motor driven element axially aligned with said hammer andanvil, a floating element located between said hammer and saidmotor-driven `element, said motor-driven element having a pair of drivepins therefor, said floating element being slidable on said drive pinsand carrying said hammer pins, said floating element having cam coactionwith said hammer element for retracting said hammer pins in relation tosaid hammer, and having further cam coaction with said anvil forreturning said hammer pins into the path of movement of said anvil.

5. An impact mechanism comprising a rotary anvil, a hammer rotatable inrelation thereto, means for driving said anvil from said hammer and forreleasing it therefrom comprising an element carried by said hammer,means independent of centrifugal force for moving said element into thepath of rotation of said anvil, said means comprising a cam actuatedelement and a hydraulic connection between said cam actuated element andsaid rst element, said hydraulic means being responsive to said camactuated element for effecting removal of said first element from suchpath after delivery of an impact from said hammer to said anvil.

6. An impact mechanism comprising a rotary anvil, a rotatable hammer,means for driving said anvil from said hammer comprising pist0n andcylinder mechanism, the cylinder thereof having an opening in a wallthereof, a plunger slidable in said opening into and out of engagementwith said anvil, and cam means operatively connected to the piston formoving said piston in one direction for extending said plunger to engagesaid anvil to deliver an impact, and for moving it in the oppositedirection for effecting removal of said plunger from engagement withsaid anvil upon predetermined resistance to torque by said anvil. Y

7. An impact mechanism comprising a rotary anvil having a pair ofradially extending arms adjacent one end, a hammer rotatable about theanvil adjacent the arms and movable axially of the anvil, at least oneimpact pin carried by the hammer and movable with the hammer into andout of the path of movement of the arms, a cam plate rotatable about theanvil between the arms and the hammer, cams on the cam plate and on thehammer adapted to move the hammer away from the arms and retract theimpact pins out of the path of movement of the arms, means to impartrotary motion to the hammer and to the cam plate and means between thehammer and the end of the anvil opposite the arms to move the hammer andproject the impact pins into the path of movement of the arms.

8. An impact mechanism comprising a rotatable anvil, ar'otatable hammeradjacent the anvil, an impact element carried by said hammer and movableinto and out of the rotative path of the anvil, a motor drivenelement,cam means between the motor driven element and the hammer for rotatingthe hammer and for retracting the impact element out of the rotativepath of the anvil, and cam means on the anvil for advancing the impactelement into the rotative path of the anvil.

9. An impact mechanism comprising a rotatable anvil having a pair ofstriking faces, a rotatable hammer adjacent the anvil, a pair of impactelements carried by said hammer and movable into and out of the rotativepath of the anvil striking faces, a motor driven element, cam meansbetween the motor driven element and the hammer for rotating the hammerand for retracting the impact elements out of the rotative path of theanvil striking faces, and cam means on the anvil for advancing theimpact elements into the rotative path of the anvil striking faces.

10. An impact mechanism comprising a rotatable anvil, a rotatable hammeradjacent the anvil, an impact element carried for rotation by saidhammer and slidable with respect to the hammer into and out of therotative path of the anvil, a motor driven element connected to saidimpact element for moving said impact element into and out of therotative path of the anvil, cam means between the motor driven elementand the hammer for rotating the hammer and for moving the motor drivenelement with respect to the hammer for retracting the impact element outof the rotative path of the anvil, and cam means between the motordriven element and the anvil for moving the motor driven element foradvancing the impact element into the rotative path of the anvil.

1l. An impact mechanism comprismg a rotatable anvil, a rotatable hammeradjacent the anvil, an impact element carried for rotation by saidhammer and slidable with respect to the hammer into and out of therotative path of the anvil, a motor driven element, a hydraulicconnection between the impact element and the motor driven element formoving said impact element into and out of the rotative path of theanvil, cam means between the motor driven element and the hammer forrotating the hammer and for moving the motor driven element with respectto the hammer for retracting the impact element out of the rotative pathof the anvil, and cam means between the motor driven element and theanvil for moving the motor driven element for advancing the impactelement into the rotative path of the anvil.

l2. An impact mechanism comprising a rotatable anvil, a rotatable hammeradjacent the anvil, an impact element carrie-d for rotation by saidhammer and slidable with respect to the hammer into and out of therotative path of the anvil, a motor driven element mechanicallyconnected to the impact element for moving the impact element into andout of the rotative path of the anvil, cam means between the motordriven element and the hammer for rotating the hammer and for moving themotor driven element with respect to the hammer for retracting theimpact element out of the rotative path of the anvil, and cam meansbetween the motor driven element and the anvil for moving the motordriven element for advancing the impact element into the rotative pathof the anvil.

13. An impact mechanism comprising a rotatable anvil, a rotatable hammeradjacent the anvil,. an impact element rigidly carried by the hammer andmovable therewith, a motor driven element, cam means between the motordriven element and the hammer for rotating the harnmer and for shiftingthe hammer to retract the impact element out of the rotative path of theanvil, and cam means between the anvil and the hammer for shifting thehammer to advance the impact element into the rotative path of theanvil.

14. An impact mechanism comprising a shaft mounted to rotate about itslongitudinal axis, an anvil fixed to the shaft intermediate its ends andextending radially therefrom, a hammer mounted for rotation on the shaftadjacent the anvil; an impact element carried by said ham- Amer andmovable into and out of the rotative `of the rotative pathof the anvil,and cam means on the shaft for advancing the impact element into therotative path of the anvil. i

. CLIFFORD E. FITCH.

REFERENCES CITED The following references are of record 1n the file ofthis patent:V

UNITED STATES PATENTS `Number Name Date Y 2,061,843 Muner NOV. 24, 19362,339,530 Van Sittert et al. Jan. 18, 1944 2,339,531 Van Sittert et al.Jan. 18, 1944:

